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to liave retained a lively interest in tecliniciil applications of .seientitic knowledge^ 

 and often rendered valnable services to his country in such matters. For a long 

 time he liad oversiglit of the manufacture of saltpeter and gunpowder for the 

 French government, and it is remarlied that during this period the gunpowder of 

 France was the Ijest in the world, while after his death it became much inferior. 

 We can scarcely find a better answer to those who would have us think that an 

 interest in technical ajjplications is lieneath the dignity of those who are devoted 

 to the development of the higher departments of science. We find, on the con- 

 trary, that scientific men of the very liighest rank have shown great interest in 

 the material advantages whicii would result from their discoveries and have 

 frequently taken time for the careful study of technical problems. While the 

 absorbing consideration of material results, which is recpiired of those who are 

 engaged in technical pursuits, is undoubtedly incompatible with any high scientific 

 attainment, I l)elieve that the scientist who o'^casionally studies carefully and 

 thoroughly some technical application of his science will lind that his mental 

 horizon has been l)roadened l)y the process. We have too many men nowadays 

 who are so ai)sorbcd in some narrcnv corner of their s^'ience as to lose all breadth 

 of view and all true sense of relative value and importance in scientific work, 

 and who become one-sided and seriously dwarfed in character. It is, after all, 

 important that one should be a man, and retain broad human interests as well a* 

 that he should attain high rank as a scientist. 



In speaking of Lavoisier's work in pure science I shall not attcmj)! an 

 exhaustive catalogue of his researches, for it is not my })urpose to give a history 

 of his life, but rather, if possible, to gain a clear conception of his character and 

 his work and of the rebition which these bear to the dcveh>{)raent of the science 

 of chemistry. 



The fir-t work in which we can see some clear relation to his later achieve- 

 ments was published in the memoirs of the Paris Academy for 1770. It con- 

 cerned the conversion of water into earth. The mere fact that such a topic 

 should re(juire careful experiment and serious discussion gives us a glimpse of 

 how very radically different from ours was the o|)inion of the best science of that 

 day upon such fundamental subjects as the indestructibility ami iuterconverti- 

 bility of matter. From the earliest times it had been believed that water may, 

 under various conditions, be converted into earth. In later times it was thought 

 that this view had been confirmed by the work of many careful experimenters. 

 Glass vessels were almost universally used for the distillation and evaporation of 

 water, and many different observers found that even water which had been 

 repeatedly distiMed left behind, on eva])oration, small amounts of earthy matter 



